Common to have to disable C-State to keep OC'd i7 6700K stable at idle?

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VirtualMirage

Limp Gawd
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Nov 29, 2011
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I've done some digging but haven't really come up with a conclusive answer. I decided recently after breaking in my new build to try and OC my processor. Overclocking these Skylake CPUs is a bit different than what I am used to with Ivy Bridge and older.

Long story short, on my i7 6700k I appear to have a stable OC of 4.5GHz (45x multiplier) with a manual voltage core setting of 1.25v. Without tinkering with LLC (which is disabled with manual voltage settings), I didn't have much luck leaving the voltage to auto and having the motherboard work the magic. I could potentially push it harder but haven't tried since, so far, I am happy with my results.

I've done long stress tests, repeat benchmarks, heavy gaming, etc...the CPU appears to be rock solid under load. No hiccups, no high temps, nothing. But when the OS is at the desktop doing nothing, after about 10-20 minutes of idling it will crash, rebooting the PC. I am running Windows 10 and the Power Options is set to High Performance. The machine is not set to go to sleep nor hibernate. The only thing that goes to sleep is the monitor.

Having done some digging, I see that others that had similar issues turned off C-State in the BIOS. This appeared to resolve their issue. I decided to do the same and, so far, the system seems to be running rock solid being powered on 24/7. The expense, of course, is about 10-20 watts more power being consumed around idle, but even then I am at 90w or less when idling.

I guess my question to you is, for those that have overclocked their Skylake CPUs:

Did you have to do the same thing?

If not, is there something I can do to increase the stability at idle with C-State enabled?

It's not a make or break deal. I just figured if I could still manage to save a few watts for the majority of the day when it isn't doing much, it would be nice.

Thanks!
 
10 or 20 watts i wouldnt be to worried about.....these older rigs like mine its worth keeping on. Those newer rigs are so much more power efficient i be tempted to leave it off as well
 
Have you tried enabling the C-states and using an offset or adaptive Vcore? I was also under the impression that C-states were not compatible with the High Performance power profile.
 
rastaban said:
Have you tried enabling the C-states and using an offset or adaptive Vcore? I was also under the impression that C-states were not compatible with the High Performance power profile.
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By default the motherboard was set to adaptive, but it didn't seem to overclock very well. I guess I could have fiddled with the LLC, but I didn't feel like it. Offset, if I recall correctly, works along with adaptive voltage, so that is out of the question. Doing some research, there wasn't a huge jump in power consumption when using a manual, fixed voltage, versus adaptive. In fact, I want to say my CPU is using less voltage under load than it was under adaptive. But because of the large swing in voltage changes, due to the LLC setting defaulting to the most linient (level 5 for AsRock), it had some stability issues under certain loads.

As for C-State not being compatible with High Performance power profile, that I am not aware of. I would think that if the CPU's power profile is set to run at full speed via Windows settings, then C-state should know not to kick in. I could be wrong.
 
Nasgul said:
Is C-State......EIST.

I leave it on, my CPU goes from 800MHz to 4,500MHz, the rated TB is 3.9GHz but didn't have to fiddle with the settings in the BIOS, it was done automatically by the ASUS software.

Your CPU should to 4.7GHz easy.
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C-State and EIST are two different things but try to achieve similar goals. EIST effects the clock speed of the CPU, ramping it up and down as needed in an effort to conserve power. C-State can work alongside that or by itself, but it tries to save power by reducing and ramping up voltage when needed. This is a pretty generic explanation and someone else might be able to flesh it out better. As for my system, I know C-State is disabled, as I mentioned earlier, but I believe I still have EIST enabled. But since I have the power profile in Windows set to High Performance, this effectively prevents EIST from kicking in since the power profile will keep the clock speed at max at all times.

It probably can go to 4.7GHz with little effort, but for now I am happy with 4.5GHz. I might try and go higher later, but I like finding a balance between extra performance but at minimal increase in extra power consumption, which equals heat. I've read quite a few people having to start cranking up their voltage at around 4.6 GHz and above. From what I have seen, so far, the voltage setting I have set at 4.5 GHz is already lower than what many others have theirs set at. While I have it set to 1.25v in the BIOS, AsRock's Fstream utility reports it being at around 1.26v when doing nothing and will climb up to about 1.29v when doing a stress test, such as Intel's XTU.
 
I always disable C states and other power save features when overclocking.

Once I challenged myself to get my OC stable using the powersave features, and I was successful, it took a lot of tinkering with the adaptive voltages. I think that was on a 4970K @ 4.5GHz on air.

But the way I look at it, I am not OCing to save power/money. My main rig is not a 24/7 rig, I build low power machines for 24/7 tasks; like my NAS.
 
Bun-Bun said:
I always disable C states and other power save features when overclocking.

Once I challenged myself to get my OC stable using the powersave features, and I was successful, it took a lot of tinkering with the adaptive voltages. I think that was on a 4970K @ 4.5GHz on air.

But the way I look at it, I am not OCing to save power/money. My main rig is not a 24/7 rig, I build low power machines for 24/7 tasks; like my NAS.
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This is my main machine which stays on 24/7 for various reasons. At the very least, even with C-state off, it still consumes less power at idle than the machine it replaced. So I at least have that going for me.
 
See if you can move some of your reasons to a RPI or something. I use a RPI as my media downloader and IRC server.

But like you said, these new chips are pretty efficient. I wouldn't worry about it.
 
I do have a home server that I use on occasion, was mainly for just doing backups and testing out VM server configurations, but it is an older AMD Phenom II X4. At idle with 5 hard drives, it consumes just as much, if not a little more than what my main machine does. So I figured, what's the point in keeping it on, especially when the other machine still needs to be on at night for backups and other miscellaneous maintenance I have scheduled (along with having to keep two UPS running). So I decided to power it off and invest in a USB 3.0 SATA hard drive dock and I do my backups to that, alternating drives in a safe. I was doing cloud backups but I have in excess of 1TB and every time I hop on the unlimited storage bandwagon with someone they decide to retract that capability and restrict you to 1 TB (Bitcasa, Microsoft, etc.). So I ended up going back to local backups for my main stuff. Besides, working in IT, I have always been of the mentality that the fewer times you power cycle the machine the fewer issues you have with it.
 
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